In this photo released by the official website of the office of the Iranian Presidency, Iran's President Hassan Rouhani, right, speaks with European Union's foreign policy chief Catherine Ashton, left, in Tehran, Iran, Sunday, March 9, 2014. An unidentified interpreter sits center.

SULAIMANIYEH, Iraq — Iran certainly seems and sounds different eight months into President Hassan Rouhani's term. Promising an "end to extremism," Mr. Rouhani signed an interim nuclear deal with world powers months ago, and now Tehran is pushing ahead on a final agreement.

Catherine Ashton, the European Union's foreign policy chief, met the president today on a visit to Tehran, her first since her appointment in 2009.

So how sustainable is the diplomatic shift if Rouhani is still struggling to outmaneuver Iranian hardliners who chant “Death to America"?

That question absorbed an expert panel at the Sulaimani Forum in northern Iraq this week. Iraqi Foreign Minister Hoshyar Zebari, who as an Iraqi Kurdish leader has worked with Iran's leadership for decades, thinks the change runs deep.

“We have seen this diplomatic shift, and I can say from my position, it is genuine, it is serious, and they mean business,” he said, addressing the panel at the American University of Iraq, Sulaimani. “They are worried more than anything else about the rise of radicalism, of sectarianism, of the Shia-Sunni rift.”

Panelists outlined five factors that will determine the staying power of Rouhani's change.

1. From the very top, Iran is committed to change.

Skeptics charge that Iran's recent moves are only a sign of angling for advantage. Yet Iran's push for moderation is "not tactical, but a genuine one,” said Ahmad Sadeghi, the deputy head of the Institute for Political and International Studies (IPIS), the think tank of Iran’s Foreign Ministry.

An Iranian leader has not “had such support from above and below" since the 1979 Islamic revolution, Mr. Sadeghi said. Rouhani's victory was a result of “consensus building between the people and elite.”

Not everyone is on board. In the past week, Rouhani has warned the Revolutionary Guard against missile launches and shrill anti-Western rhetoric, and he is locked in battle over levels of cultural openness in Iran.

When asked if Rouhani would prevail, Sadeghi replied that as long as the talks have the support of Supreme Leader Ayatollah Ali Khamenei, even critics will back them, albeit reluctantly.

2. Iran is adapting to regional changes.

The regional upheaval of the last few years has changed the balance of power, and Iran is going through a “strategic recalculation," said Robin Wright, a journalist who visited Iran recently and first reported on Iran 41 years ago.

Nearly 10 years ago, Iran was the leader of a powerful arc of Shiite influence that stretched from Tehran to Baghdad to Damascus to Beirut. But with Al Qaeda franchises cropping up and sectarian divisions tearing throughout the region, that is no longer the case, said Ms. Wright, the author of several books on Iran and the Middle East. The US withdrawal from Iraq and Afghanistan has robbed Iran of the first line of defense against Sunni influence and insurgencies.

“The irony is the US buffer created a decade ago has disappeared and Iran, I think, for all its pride and achievements, actually feels a little bit vulnerable,” Wright said.

The result is that Iran “suddenly” finds itself sharing many strategic aims with the US, like solving the nuclear issue and stopping the spread of Sunni radicalism.

“There is something much more profound than a new election with a new president,” Wright said. “I believe the 'Government of God', even though it has lofty ideological goals, has plummeted to earth and is very realistic."

3. Principles alone can't sustain a country.

The Islamic Republic has not yet decided if it is a country or a cause – a choice first outlined by former Secretary of State Henry Kissinger.

Ideological “principlists” emphasize continued resistance against the US and Israel. But Rouhani and Foreign Minister Mohammad Javad Zarif reflect popular will for prioritizing national and economic interests, said Karim Sadjadpour, an Iran analyst with the Carnegie Endowment for International Peace.

“Both of these groups within Iran are loyal soldiers of the revolution, and both want to preserve the Islamic Republic,” said Mr. Sadjadpour. The debate “is going to play out for several years.”

4. America is cautiously welcoming.

Ken Pollack, who was former President Bill Clinton’s Persian Gulf director when the US sent overtures to Iran in the late 1990s, said it was “wonderful” to hear such conciliatory words from Sadeghi of the Iranian think tank.

President Barack Obama is "eager to explore" if a nuclear deal is possible, and a wider rapprochement after that, said Mr. Pollack, a senior fellow at the Brookings Institute and the author of “Unthinkable: Iran, the Bomb, and American Strategy.”

“It really does start with that nuclear deal. If we can get that, there is a hope that can be part of – a door to – a wider relationship with Iran," he said.

A wide gap remains between the two countries' expectations: Will Iran cap its nuclear program, and at what point? How much will crippling sanctions be lifted? And how can there be trust, with poisonous domestic politics on both sides?

But fear of being perceived as the reason the deal fails seems to be holding back spoilers on either side.

“The country that kills this deal, that so much of the world is interested and invested in, is going to be seen as the bad guys,” Pollack said.

5. Iran wants to regain powerhouse status.

In 1978, the year before the Islamic revolution, oil-rich Iran’s GDP was double that of Turkey. Today it is half that of Turkey, said CEIP’s Sadjadpour, saying that a focus on ideology had hampered Iran's progress.

Iran’s human capital, “civilizational heft” (some 5,000 years of Persian history), and natural resources means it can be a major global player and, like Turkey, be a member of the G20, said Sadjadpour.

“But as long as Iran continues to put these ideological pursuits first, I think they will remain only a regional player – if not a regional spoiler – rather than a global player.”